Field
Implementations disclosed herein generally relate to polishing articles and methods for manufacturing polishing articles used in polishing processes. More specifically, implementations disclosed herein relate to porous polishing pads produced by processes that yield improved polishing pad properties and performance, including tunable performance.
Description of the Related Art
Chemical mechanical polishing (CMP) is a conventional process used in many different industries to planarize surfaces of substrates. In the semiconductor industry, uniformity of polishing and planarization has become increasingly significant as device feature sizes continue to decrease. During a CMP process, a substrate, such as a silicon wafer, is mounted on a carrier head with the device surface placed against a rotating polishing pad. The carrier head provides a controllable load on the substrate to push the device surface against the polishing pad. A polishing liquid, such as slurry with abrasive particles, is typically supplied to the surface of the moving polishing pad and polishing head. The polishing pad and polishing head apply mechanical energy to the substrate, while the pad also helps to control the transport of slurry, which interacts with the substrate during the polishing process.
A conventional polishing pad is typically made by molding, casting or sintering polymeric materials that include polyurethane materials. In the case of molding, polishing pads can be made one at a time, e.g., by injection molding. In the case of casting, the liquid precursor is cast and cured into a cake, which is subsequently sliced into individual pad pieces. These pad pieces can then be machined to a final thickness. Pad surface features, including grooves, which aid in slurry transport, can be machined into the polishing surface, or be formed as part of the injection molding process.
Polishing pads made of harder materials often exhibit high removal rates and have long useful pad life, but undesirably tend to form numerous scratches on the substrate being polished. Polishing pads made of softer materials exhibit low scratching of substrates, but tend to exhibit lower removal rates and have shorter useful pad life.
In the case of porous polishing pads, open pore structures may be introduced into the pad via methods including poromerics and closed pore structures may be introduced into the pad via methods including blending with microspheres, frothing, microcellular foaming, blending with water-soluble spherical particles, and embedding with mineral oil. These methods of manufacturing polishing pads are expensive and time consuming, and often yield non-uniform polishing results due to the difficulties in the production and control of the pad surface feature dimensions. Non-uniformity has become increasingly significant as the dimensions of IC devices and feature sizes continue to shrink.
Accordingly, there remains a need in the art for polishing pads and methods of manufacturing polishing pads that provide uniform removal rates, have extended pad life, and minimizes scratching of the polished substrate.